Vehicle Clustering Phenomenon in Automatic Materials Handling Systems in 300mm Semiconductor Manufacturing

During design and implementation of the automatic materials handling system (AMHS) for a local 300mm semiconductor wafer fab (semiconductor fabrication plant), we observed and found an interesting phenomenon Vehicle Clustering Phenomenon (VCP) from the dynamics of automated vehicles: As time evolves, the distance between any two adjacent vehicles usually becomes very close enough as if all the vehicles are a long train of vehicles running around the loop. The overall performance thus deteriorates due to this phenomenon. This paper explores the causes of the VCP problem and clarifies its impacts to automatic materials handling operations in 300mm semiconductor manufacturing.